Carbon−Proton Chemical Shift Correlation in Solid-State NMR by Through-Bond Multiple-Quantum Spectroscopy

Abstract

A new two-dimensional NMR carbon−proton chemical shift correlation experiment, the MAS-J-HMQC experiment, is proposed for natural abundance rotating solids. The magnetization transfer used to obtain the correlations is based on scalar heteronuclear J couplings. The 2D map provides through-bond chemical shift correlations between directly bonded proton−carbon pairs in a way similar to that in corresponding high-resolution liquid-state experiments. The transfer through J coupling is shown to be efficient and more selective than those based on heteronuclear dipolar couplings. The experiment, which works at high MAS spinning frequencies, yields the unambiguous assignment of the proton resonances. The experiment is demonstrated on several organic compounds.

Understanding Sterol‐Membrane Interactions, Part II: Complete 1H and 13C Assignments by Solid‐State NMR Spectroscopy and Determination of the Hydrogen‐Bonding Partners of Cholesterol in a Lipid Bilayer

“…[43] However, fast relaxation processes have so far prevented long-range J-couplingbased experiments and the observation of multiple-bond connectivity. Furthermore, for reasons of sensitivity, 13 C- 13 C homonuclear correlation techniques [44][45][46] are rarely applicable to natural abundance materials in membrane samples. One way to recover skeletal information is to transfer magnetization through dipolar coupling to obtain through-space correlation, that is, cross peaks between bound and nonbound pairs.…”

Unexpected effects of third-order cross-terms in heteronuclear spin systems under simultaneous radio-frequency irradiation and magic-angle spinning NMR

“…However, it is only with the development of 1 H homonuclear decoupling schemes suitable for application under moderate to fast MAS frequencies, e.g., Frequency-Switched Lee-Goldburg (FSLG), 5 Phase-Modulated Lee-Goldburg (PMLG), 6 and DUMBO, 7 coupled with advances in RF consoles, that such experiments have started to be more widely employed. 8,9 For example, 13 C, 1 H heteronuclear correlation (HETCOR) experiments at moderate to fast MAS frequencies 10,11 have been widely applied to a variety of significant material types, such as proteins, 12,13 pharmaceuticals, 14,15 silica-supported catalytic complexes, 16,17 organic-templated microporous materials, 18 inorganic-organic hybrid materials, 19 as well as chemical problems, such as the characterisation of weak hydrogen bonding in sugars 20 and the solution of structures from powder diffraction data. 21 Heteronuclear 13 C{ 1 H} spin-echo experiments employing 1 H homonuclear decoupling during the a) Author to whom correspondence should be addressed.…”

Rapid Analysis of Organic Compounds by Proton‐Detected Heteronuclear Correlation NMR Spectroscopy with 40 kHz Magic‐Angle Spinning

“…20 mg of sample). [6,7] Inverse proton detection at 30-kHz MAS rate has been demonstrated on a polymer and a 13 C-labeled heptapeptide, with sensitivity enhanced approximately twoto threefold. [8] At even faster MAS rates (ca.…”

“…[6,7] Fast MAS dramatically reduces the effective 1 H-1 H dipolar couplings and separates CH n groups from other protons during cross polarization (without the need for homonuclear decoupling). [24] Meanwhile, quaternary carbon atoms correlate to protons two and three bonds away in the same spectrum.…”

“…In contrast, a separate MAS-J-HMQC experiment is necessary to establish multiple-bond correlations by using a very long evolution period, which leads to significant signal loss. [6,7] Longer-range correlations are very weak in fast-MAS HETCOR and can only be observed with additional signal accumulation. When long-range contacts are sought, for instance, for the determination of atomic-resolution structure, [25] they can be readily reestablished by inserting a 1 H-1 H dipolar recoupling element in the pulse sequence.…”